In a parts mounting process of mounting electronic parts on a substrate, a substrate is positioned and retained while a downside of the substrate is supported by a lower receiving section. A lower receiving pin technique for bringing a plurality of lower receiving pins in contact with a downside of a substrate and supporting the substrate has widely been used as the technique for receiving a downside of a substrate. A method which has hitherto been known as a pin arrangement method for use with the lower receiving pin technique is to removably fit backup pins (lower receiving pins) upright into pin insert holes opened in a lattice pattern in a backup base (a lower receiving base) (see; for instance, Patent Documents 1 and 2). According to the related art technique described in connection with the examples of Patent Documents, an area in the backup base where the substrate is not placed is used as a stock area for housing backup pins that do not support a substrate. In Patent Document 1, a transfer sequence is set in consideration of a distance of a transfer location, where backup pins are transferred, from the stock area, thereby hindering the backup pins from interfering with each other during transfer operation.